Absolutist opposition to suicide no matter how prolonged or severe the suffering is right up there with torture as to why humans are by far the most savage and monstrous animal species.
Lions slowly munching on their prey alive over several hours have nothing on humans who arrange for intolerable suffering to extend over years.
I don't have absolutist opposition to suicide. But what are we gonna do, criminalize it? That would be literally the most unenforceable law. That doesn't mean we should facilitate the act of suicide.
Suicide is illegal in some jurisdictions. It matters more than you seem to think, because there's prosecution of attempted suicide as well as of assisting suicide (which can also be illegal if suicide itself is not).
Lions slowly munching on their prey alive over several hours have nothing on humans who arrange for intolerable suffering to extend over years.